在嵌套的MongoDB字段上创建索引？
您可以为此使用dot（。）表示法。首先让我们创建一个包含文档的集合-
> db.createIndexOnNestedFieldDemo.insertOne(
{"UserDetails":{"UserPersonalDetails":{"UserFirstName":"John","UserLastName":"Smith"}}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce929c778f00858fb12e916")
}
>
> db.createIndexOnNestedFieldDemo.insertOne( {"UserDetails":{"UserPersonalDetails":{"UserFirstName":"Chris","UserLastName":"Brown"}}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce929d678f00858fb12e917")
}
> db.createIndexOnNestedFieldDemo.insertOne( {"UserDetails":{"UserPersonalDetails":{"UserFirstName":"David","UserLastName":"Miller"}}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce929e378f00858fb12e918")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.createIndexOnNestedFieldDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5ce929c778f00858fb12e916"),
"UserDetails" : {
"UserPersonalDetails" : {
"UserFirstName" : "John",
"UserLastName" : "Smith"
}
}
}
{
"_id" : ObjectId("5ce929d678f00858fb12e917"),
"UserDetails" : {
"UserPersonalDetails" : {
"UserFirstName" : "Chris",
"UserLastName" : "Brown"
}
}
}
{
"_id" : ObjectId("5ce929e378f00858fb12e918"),
"UserDetails" : {
"UserPersonalDetails" : {
"UserFirstName" : "David",
"UserLastName" : "Miller"
}
}
}以下是在嵌套字段上创建索引的查询-
>db.createIndexOnNestedFieldDemo.createIndex({"UserDetails.UserPersonalDetails.UserLastName":1});这将产生以下输出-
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}